1. Field of the Invention
This invention relates to a process of polymerizing acrylic esters and, more specifically, to initiators which are useful therein.
2. Background
U.S. Pat. Nos. 4,414,372; 4,417,034; 4,508,880; 4,524,196; 4,581,428; 4,588,795; 4,598,161; 4,605,716; 4,622,372; 4,656,233; 4,681,918; and 4,711,942; and commonly assigned U.S. patent application Ser. No. 004,831 filed Jan. 13, 1987, referred to hereinafter as "the aforesaid patents and patent applications", disclose processes for polymerizing an acrylic or maleimide monomer to a "living" polymer in the presence of:
(i) an initiator having at least one initiating site and which is a tetracoordinate organo(Si, Sn or Ge) compound, including such compound having at least one oxygen, nitrogen or sulfur atom attached to the Si, Sn or Ge; and
(ii) a co-catalyst which is a source of fluoride, bifluoride, cyanide or azide ions or a suitable Lewis acid, Lewis base or selected oxyanion. Such polymerization processes have become known in the art as Group Transfer Polymerization (Webster et al., "Group Transfer Polymerization--A New and Versatile Kind of Addition Polymerization", J. Am. Chem. Soc. 105, 5706 (1983)).
Additional details regarding Group Transfer Polymerization can be obtained from the aforesaid patents and patent applications, the disclosures of which are hereby incorporated by reference.
It is an object of this invention to provide additional silicon-containing compounds which are useful as initiators in acrylic ester polymerization. This and other objects will become apparent hereinafter.